1. Field of the Invention
The present invention relates to a shadow mask/frame assembly for a color cathode ray tube (CRT), and more particularly, to a shadow mask/frame assembly for a color cathode ray tube in which a frame installed at a panel is improved.
2. Description of the Related Art
FIGS. 1 and 2 are a sectional view of a typical color CRT and an exploded perspective view showing a shadow mask frame assembly for a color CRT installed at the color CRT, respectively. Referring to the drawings, a typical color CRT includes a panel 11 on an inner surface of which a fluorescent film 11a is formed, and a funnel 30 coupled to the panel 11. An electron gun 15 is installed at a neck portion 14 of the funnel 30 and a deflection yoke 20 is installed at a cone portion 12 of the funnel 30.
Also, the typical color CRT has a shadow mask frame 10. The shadow mask frame 10 includes a shadow mask 16 installed to be separated a predetermined distance from the fluorescent film 11 a, a frame 17 supporting the shadow mask 16, and an inner shield 21 of a rectangular funnel shape which is coupled to the frame 17. A skirt portion 17a for supporting the shadow mask 16 by being welded thereto is formed at the frame 17. A flange portion 17b bent toward the inner side is extended from the skirt portion 17a so that the flange portion 17b is coupled to the inner shield 21.
The shadow mask 16 includes a hole portion 16c having a plurality of electron beam passing holes, a hole-free portion 16b extending from the edge of the hole portion 16c, and a bending portion 16a extending downward at a right angle from the hole-free portion 16b and fixed to the skirt portion 17a. 
A hook spring 19 fixed to the outer surface of the frame 17 is coupled to a stud 18 installed on the inner surface of the panel 11 and the shadow mask frame assembly 10 is installed at the inner surface of the panel 11.
The weight of the frame 17 increases as the size of the color CRT increases. Typically, a panel member having a thickness of about 1.2 mm is used for the color CRT less than 14 inches whereas a thin panel having a thickness of about 0.8 mm is used for a color CRT about 14-29 inches to reduce the weight thereof. When these thin panels are used, the support force of the frame 17 to the shadow mask 16 decreases so that the shadow mask 16 is deformed when an external impact is applied or during the manufacturing process.
Also, an electron beam emitted from the electron gun is selectively deflected by the deflection yoke 20 and passes through the holes of the shadow mask 16 for color selection, and excites the fluorescent film 11a. Here, the electron beam input to the edge of the shadow mask 16 is reflected on the flange portion 17b, generating diffusion-reflection. Furthermore, although not shown in the drawings, the diffused electron beam passes through the electron beam passing hole of the shadow mask 16 and excites an undesired pixel. To solve the above problems, a method of bending an end portion of the flange portion 17b at a predetermined angle toward the shadow mask 16 has been suggested. However, the sufficient structural strength of the frame 17 and sufficient prevention of the diffusion-reflection cannot be expected.
To solve the above problems, it is an objective of the present invention to provide a shadow mask/frame assembly having an improved frame structure so that the shadow mask can be prevented from being deformed by an external impact and the diffusion-reflection can be prevented.
Accordingly, to achieve the above objective, there is provided a shadow mask/frame assembly for a color CRT which comprises a shadow mask including a hole portion having a predetermined curvature where a plurality of electron beam passing holes are formed and a bending portion extending from the edge of the hole portion by being bent at a predetermined angle, and a frame including a skirt portion coupled to the bending portion of the shadow mask, a flange portion extending from the skirt portion by being bent at a right angle thereto, a connection portion extending downward from the flange portion, and an extension portion extending from the connection portion, parallel to the flange portion.
It is preferable in the present invention that an end portion of the extension portion has a knife edge shape for allowing an electron beam colliding with the extension portion to be diffusely reflected to the area except for the hole portion.